The Vampire Diaries ran from 2009 to 2017. During its second season members of the original family of vampires, The Mikaelsons, started trickling in. Eventually The Originals got its own spin-off set in New Orleans, LA and over the next few years characters made their ways back and forth.

Klaus Mikaelson is first mentioned in the second season of TVD in the episode "Rose," the same episode in which Elijah sashayed onto the screen. However, Klaus doesn't grace Mystic Falls with his physical presence until the aptly titled episode "Klaus." Rebekah doesn't show up until season three in "The End of the Affair." Season three's "Bringing Out the Dead" also introduced us to Kol and Finn.

"The Originals:" Backdoor pilot where we meet Hayley Marshall and find out that she and Klaus were closer than we thought.TVD 4.20

"Bloodletting:" Tyler visits New Orleans and his old friend Hayley to get revenge on Klaus. Does Klaus ever get visitors that aren't looking for revenge?TO 1.07

"The River in Reverse:" Tyler is still in NOLA being an asshole.TO 1.08

Also the episode that Klaroline shippers
got early Christmas presents.

"500 Years of Solitude:" TVD's 100th episode. While Katherine is dying she hallucinates Elijah. Klaus and Rebekah visit Mystic Falls and drop in on old friends.TVD 5.11

"Red Door:" We learn the truth about Tatia's backstory. I don't know if this is technically a crossover since Tatia isn't a member of TVD scooby gang, but Nina Dobrev does play both characters so I included it.TO 2.05

"Moonlight on the Bayou:" Stefan visits New Orleans to seek sanctuary from hunter Rayna Cruz.TVD 7.14

"A Streetcar Named Desire:" Stefan is still hiding in The Big Easy.TO 3.14

"Behind the Black Horizon:" Freya is kidnapped and taken to Mystic Falls. Elijah and Finn show up to rescue her. Matt Donovan is there too. Because he's always there.TO 3.17

I'll keep this post updated as Mystic Falls natives make their way over for Mardi Gras with the Mikaelsons.